Portion of chair



FIG. 1 is a front view of a chair showing my new design;

FIG. 2 is a rear view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a left side view thereof; and,

FIG. 5 is a top view thereof.

The broken lines in the drawings represent environmental subject matter and form no part of the claimed design. 

The ornamental design for a portion of chair, as shown and described. 